changing membrane potential

Question 1

what is depolarisation

Answer 1

less negative, increase in the potential

Question 2

what is hyper polarisation

Answer 2

more negative than resting value

Question 3

how nictonic Ach changes membrane potential

Answer 3

it is selective for Na+ and k+. binding of Ach opens the channel and Na+ diffuses in and k+ diffuses out but anions cannot. this moves membrane to 0mv - depolarisation. when the diffusion of both is equal the membrane potential = 0

Question 4

types of channels

Answer 4

ligand gates, voltage gated and mechanically gated (changes in pressure)

Question 5

what are excitatory synapses

Answer 5

when ligand gated channels are opened the cell is depolarised resulting in a change called excitatory-post synaptic potential

Question 6

how does the size of the EPSP affect the action potential

Answer 6

size is dependant on the amount of neurotransmitter and it is longer than an action potential. transmitter include glutamate and ach

Question 7

what are inhibitory synapses

Answer 7

inhibitory neurotransmitter cause hyper polarisation by opening k+ and cl- channels. transmitter include glycine and GABA which are both amino acids

Question 8

what is slow transmission

Answer 8

G protein has slow transmission of info into cell because requires activation of second messenger and whole cell must be activated

Question 9

what is fast transmission

Answer 9

binding og ligand to channel causing it to open. much quicker than g protein

Question 10

factors affecting membrane potential

Answer 10

changes in ion concentration - k+ conc outside of cell may alter excitability of heart
electrogenic pumps- very small effect but for every 3Na+ pumped out 2k+ are pumped in

Question 11

how is the membrane potential changed

Answer 11

if the selective ion permeability is changed e.g by opening a na+ channel

Question 12

what are the equilibrium potentials or the physiological ions

Answer 12

Ek= -95mv
Ecl= -96mv
Ena= +70mv
ACa= +122mv 
this means that opening k and cl channels hyper polarises membrane and opening na and ca channels will depolarise the membrane

Question 13

what is the GHK equation

Answer 13

equation that combines all the ion permeability if more than 1 permeability is changed which in a real cell it will be. give the overall membrane permeability and if they change so will the whole membrane potential